The present invention relates to snowmobiles, and more particularly to snowmobiles with engines having air chargers such as exhaust-driven (turbo) or mechanical superchargers.
Conventionally, snowmobiles have been made small and light weight, yet have relatively powerful engines in order to appeal to the typical snowmobile driver. Because of the small size, the packaging of the components in a snowmobile is critical. However, due to its sporting nature, it is also desirable to have a snowmobile that is powered by an engine that is not only efficient and light weight, but also generates significant power for its size. So, traditionally, two cycle engines have been used to power snowmobiles. These engines have the advantage that they are powerful, yet relatively light weight and compact. One particular disadvantage to the two cycle engine is its emissionsxe2x80x94it generally exhausts more hydrocarbons and other pollutants than an equivalent four cycle engine due to cylinder charging inefficiencies and the combustion of lubricating oil, among other things. Also, the two cycle engine tends to operate at a relatively high noise level. With concern for the environment and increasing strict emissions requirements being instituted by governments, it is increasingly desirable to use four cycle engines with snowmobiles.
But a naturally aspirated four cycle engine generally produces less specific output per liter of engine displacement than does a two cycle engine. It is not practical to merely increase the engine size due to the size and weight limitations present in packaging an engine in a snowmobile. Furthermore, the typical transmission employed in a snowmobile limits the upper end of the RPM range for the engine. To increase the output of a particular four cycle engine, then, one may wish to employ an air charging system, such as a turbocharger (exhaust driven compressor) or a supercharger (mechanically driven compressor). However, a conventional air charger will require the use of a higher grade of gasoline in order to avoid detonation and pre-ignition problems (i.e. engine knock), which can over time significantly reduce the useful life of an engine. This higher grade of gasoline is not always available to a snowmobile driver along the various trails that he may travel.
Thus, it is desirable to have a snowmobile that is powered by a four cycle engine which overcomes the drawbacks of limited engine output, while still remaining relatively small and light weight. In particular, it is desirable to have an air charging system that maximizes the engine output while not requiring a premium grade of gasoline.
In its embodiments, the present invention contemplates a snowmobile having a chassis that includes a track tunnel portion having a front end, with the front end of the tunnel portion including an intercooler opening; a track located within the tunnel portion; and an engine mounted to the chassis, and including an air intake assembly and an exhaust assembly. The snowmobile also includes an air charging system; and an intercooler system including a heat exchanger being disposed adjacent to the intercooler opening, with the heat exchanger including a charge air inlet and a charge air outlet, and with the charge air inlet being in fluid communication with the air charging system and the charge air outlet being in fluid communication with the air intake assembly.
The present invention further contemplates a snowmobile having a chassis that includes a track tunnel portion having a front end, with the front end of the tunnel portion including an intercooler opening; a track located within the tunnel portion; an engine mounted to the chassis, and including an air intake assembly and an exhaust assembly; and an air charging system. The snowmobile also has an intercooler system including a first heat exchanger being disposed adjacent to the intercooler opening, with the first heat exchanger including a first intercooler fluid inlet and a first intercooler fluid outlet; a second heat exchanger being in fluid communication with the air charging system and the air intake assembly, and including a second intercooler fluid inlet in communication with the first intercooler fluid outlet and a second intercooler fluid outlet; and an intercooler fluid storage assembly in fluid communication with the second intercooler fluid outlet and the first intercooler fluid inlet.
In its embodiments, the present invention also contemplates a method of operating a snowmobile engine having an air charging assembly, an engine air intake assembly, and an engine exhaust assembly, the method comprising the steps of: compressing intake air in the air charging assembly; locating snow/ice on a heat exchanger; passing the compressed intake air through the heat exchanger to thereby transfer heat to the snow/ice; and directing the compressed intake air into the air intake assembly.
The present invention further contemplates a method of operating a snowmobile engine having an air charging assembly and an air intake assembly, the method comprising the steps of: compressing intake air in the air charging assembly; locating snow/ice on a first heat exchanger; passing an intercooler liquid through the first heat exchanger to thereby transfer heat to the snow/ice; passing the intercooler liquid through a second heat exchanger; passing the compressed intake air through the second heat exchanger to thereby transfer heat to the intercooler liquid; and directing the compressed intake air into the air intake assembly.
An advantage of an embodiment of the present invention is that a four stroke engine may be employed with a snowmobile, producing sufficient engine output, while remaining relatively small and light weight.
Another advantage of an embodiment of the present invention is that the charged air engine in the snowmobile need not require a premium grade of gasoline to operate properly.
A further advantage of an embodiment of the present invention is that the intercooler heat exchanger, by employing snow/ice to cool the charge air, is very efficient, allowing it to be relatively small and light weight. This efficiency also allows for minimum pressure loss in the charge air as it is being cooled in the heat exchanger, thus allowing for a relatively smaller size turbine in the air charger assembly while still providing sufficient pressure in the engine air intake. This allows for easier packaging of the components as well as reduced cost.
An added advantage of an embodiment of the present invention is that the engine cold start capability is improved since the engine will operate at higher compression ratios than would otherwise be possible with regular grade gasoline.
Another advantage of an embodiment of the present invention is that there is minimal turbo lag in the system since the total air volume in the engine system is kept to a minimum.
A further advantage of an embodiment of the present invention is that the intercooler system for the air charger is effective even during operation of the snowmobile under high engine load, low forward speed conditions, such as when climbing a hill.
An additional advantage of an embodiment of the present invention is that a portion of the intercooler liquid can be injected into the charge air, thus removing additional heat from the air charge.